Polishing pad and chemical mechanical polishing method

ABSTRACT

A polishing pad for chemical mechanical polishing, which has an excellent removal rate and is capable of polishing for providing excellent planarity. This polishing pad comprises 70 to 99.9 mass % of (A) a crosslinked diene elastomer and 0.1 to 30 mass % of (B) a polymer having an acid anhydride structure based on 100 mass % of the total of the above components (A) and (B) and has a specific gravity of 0.9 to 1.2.

FIELD OF THE INVENTION

[0001] The present invention relates to a polishing pad, especially apolishing pad for polishing an insulating film and a metal film, and achemical mechanical polishing method. More specifically, it relates to apolishing pad having an excellent removal rate and capable of polishingfor providing excellent planarity, especially a polishing pad having anexcellent removal rate for both an insulating film and a metal film, anda chemical mechanical polishing method.

[0002] The present invention is widely used to polish the surface of asemiconductor wafer, etc.

DESCRIPTION OF THE PRIOR ART

[0003] CMP (Chemical Mechanical Polishing) has been attracting muchattention as a polishing technique capable of forming a surface havinghigh planarity. In CMP, slurry which is an aqueous dispersion ofabrasive particles is dropped on the surface of a polishing pad fromabove while the polishing pad and the surface to be polished are broughtinto slide contact with each other.

[0004] In this CMP, the removal rate is one of the factors for greatlyaffecting productivity. It is said that this removal rate can be greatlyimproved by holding a large amount of slurry on the surface of apolishing pad.

[0005] Heretofore, CMP polishing pads have been made of foamedpolyurethane having pores of several tens of micrometers in diameter.Since polyurethane is generally inferior in water resistance, the abovepolishing pads have a durability problem. When an elastomer such asbutadiene rubber having excellent water resistance is used, the obtainedpolishing pad has poor wettability by water and a low removal rate. Whena foamed product is used to hold slurry, satisfactory planarity is notobtained.

SUMMARY OF THE INVENTION

[0006] In view of the above situation, it is an object of the presentinvention to provide a polishing pad having an excellent removal rateand capable of polishing for providing excellent planarity.

[0007] It is another object of the present invention to provide apolishing pad having an excellent removal rate for both an insulatingfilm and a metal film.

[0008] It is still another object of the present invention to provide achemical mechanical polishing method using the polishing pad of thepresent invention.

[0009] Other objects and advantages of the present invention will becomeapparent from the following description.

[0010] According to the present invention, firstly, the above objectsand advantages of the present invention are attained by a polishing padwhich comprises (A) 70 to 99.9 mass % of a crosslinked diene elastomerand (B) 0.1 to 30 mass % of a polymer having an acid anhydride structurebased on 100 mass % of the total of the above components (A) and (B) andwhich has a specific gravity of 0.9 to 1.2.

[0011] According to the present invention, secondly, the above objectsand advantages of the present invention are attained by a chemicalmechanical polishing method, comprising flattening the surface of amaterial to be polished by chemical mechanical polishing with thepolishing pad of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a sectional view of a material (wafer) to be polishedused in a chemical mechanical polishing method;

[0013]FIG. 2 are sectional views of another material to be polished bychemical mechanical polishing, wherein FIG. 2(a) is a sectional view ofthe material to be polished before polishing for the separation ofmicro-elements and FIG. 2(b) is a sectional view of the separatedmicro-elements after polishing; and

[0014]FIG. 3 are sectional views of another material to be polished bychemical mechanical polishing, wherein FIG. 3(a) is a sectional view ofthe material to be polished for flattening an interlayer insulating filmbefore polishing and FIG. 3(b) is a sectional view of the flattenedinterlayer insulating film after polishing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015] The present invention will be described in detail hereinunder.

[0016] The above “(A) crosslinked diene elastomer” is an elastomer whichcontains the polymerization unit of a diene monomer and has acrosslinked structure. The polymerization unit of a diene monomer may ormay not be hydrogenated after polymerization. The crosslinked dieneelastomer (A) contains the polymerization unit of a diene monomer in anamount of 40 to 100 mass %, more preferably 60 to 100 mass %, much morepreferably 80 to 100 mass % based on 100 mass % of the elastomer.

[0017] The crosslinked diene elastomer (A) is, for example, acrosslinked butadiene elastomer or crosslinked isoprene elastomer.Examples of the crosslinked butadiene elastomer include crosslinkedrubbers obtained by crosslinking a polymer such as butadiene rubber,1,2-polybutadiene, acrylonitrile-butadiene rubber, styrene-butadienerubber or styrene-butadiene-styrene (SBS) block copolymer, andhydrogenated polymers thereof such as SBS hydrogenated block copolymer(SEBS). These elastomers may be used alone or in combination of two ormore. Examples of the isoprene elastomer include crosslinked rubbersobtained by crosslinking a polymer such as isoprene rubber,styrene-isoprene rubber or isobutylene-isoprene rubber, and hydrogenatedproducts thereof. These elastomers may be used alone or in combinationof two or more. Out of these crosslinked diene elastomers, crosslinked1,2-polybutaidene is particularly preferred because a composition havinghigh hardness is obtained.

[0018] The crosslinking method for obtaining the above crosslinkedelastomer (A) is not particularly limited but a crosslinking agent isgenerally used for crosslinking. The crosslinking agent may be sulfur oran organic peroxide but an organic peroxide is preferred because animpurity such as sulfur is undesirable for the polishing of asemiconductor. Examples of the organic peroxide include dicumylperoxide, di-t-butyl peroxide, diethyl peroxide, diacetyl peroxide anddiacyl peroxide. They may be used alone or in combination of two ormore.

[0019] The above “(B) polymer having an acid anhydride structure” is apolymer having an acid anhydride structure represented by the followingformula (1).

[0020] The polymer having an acid anhydride structure (B) is, forexample, one of (1) a polymer having an acid anhydride structure in themain chain, (2) a polymer having an acid anhydride structure not in themain chain but only in the side chain, and (3) a polymer having an acidanhydride structure in both the main chain and the side chain.

[0021] The above polymer having an acid anhydride structure in the mainchain (1) can be obtained as a homopolymer of a monomer having an acidanhydride structure or a copolymer of a monomer having an acid anhydridestructure and a monomer having no acid anhydride structure.

[0022] The latter copolymer comprising a monomer having no acidanhydride structure contains a polymerization unit derived from amonomer having an acid anhydride structure in an amount of preferably0.1 to 40 molt, more preferably 0.5 to 30 molt, particularly preferably1.0 to 25 molt based on the total of the polymerization units of theboth monomers.

[0023] Examples of the above monomer having an acid anhydride structureinclude maleic anhydride, itaconic anhydride, citraconic anhydride andendomethylenetetrahydrophthalic anhydride. Examples of the above monomerhaving no acid anhydride structure include conjugated diene compounds,aromatic monomers and (meth)acrylate compounds.

[0024] The conjugated diene compounds include 1,3-butadiene, isoprene,2,3-dimethyl-1,3-butadiene and chloroprene, the aromatic monomersinclude styrene, α-methylstyrene, o-hydroxystyrene, m-hydroxystyrene andp-hydroxystyrene, and the (meth)acrylate compounds include methyl(meth)acrylate, ethyl (meth)acrylate, 2-hydroxymethyl (meth)acrylate,3-hydroxypropyl (meth)acrylate, dimethylaminomethyl (meth)acrylate anddimethylaminoethyl (meth)acrylate.

[0025] The above polymer having an acid anhydride structure not in themain chain but only in the side chain (2) can be obtained by modifying apolymer having no acid anhydride structure with a monomer having an acidanhydride structure. The “modification” can be realized by a method inwhich a side chain having an acid anhydride structure is added to apolymer having no acid anhydride structure by heating the polymer havingno acid anhydride structure in the presence of a monomer having an acidanhydride group and a peroxide such as hydrogen peroxide or organicperoxide, or a method in which a side chain having an acid anhydridestructure is added to a polymer having no acid anhydride structure byheating the polymer having no acid anhydride structure in the presenceof a compound having at least two acid anhydride structures in themolecule and/or a compound having an acid anhydride structure and acarboxyl group in the molecule and a catalyst such as acid, alkali ormetal catalyst.

[0026] The monomer having an acid anhydride group is used in an amountof preferably 0.1 to 150 parts by weight, more preferably 0.5 to 110parts by weight, particularly preferably 1.0 to 75 parts by weight basedon 100 parts by weight of the monomer having no acid anhydridestructure.

[0027] The above polymer having no acid anhydride structure in the mainchain is, for example, a polyolefin, diene (co)polymer, hydrogenatedproduct of a diene (co)polymer or (meth)acrylate polymer. Examples ofthe above polyolefin include polyethylene, polypropylene, polybutene,ethylene-propylene copolymer and ethylene-butene copolymer, and examplesof the above diene(co)polymer include butadiene rubber,1,2-polybutadiene, styrene-butadiene copolymer and isoprene rubber.

[0028] The above (meth)acrylate is a homopolymer or copolymer of a(meth)acrylic ester. Examples of the (meth)acrylic ester include methyl(meth)acrylate, γ-(meth)acryloxypropyl(dimethoxy)methylsilane,γ-oxypropyltrimethoxy(meth)acrylate, glycidyl (meth)acrylate,2-hydroxymethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,dimethylaminomethyl (meth)acrylate and dimethylaminoethyl(meth)acrylate.

[0029] Examples of the above monomer having an acid anhydride structureare the same as those enumerated as the monomer having an acid anhydridegroup used for the synthesis of the polymer having an acid anhydridestructure in the main chain (1).

[0030] Examples of the above compound having at least two acid anhydridestructures in the molecule include pyromellitic anhydride and3,3′,4,4′-benzophenonetetracarboxylic dianhydride, and examples of theabove compound having an acid anhydride structure and a carboxyl groupin the molecule include trimellitic anhydride.

[0031] The above polymer having an acid anhydride structure in both themain chain and the side chain (3) can be obtained by modifying the abovepolymer having an acid anhydride structure in the main chain (1) with amonomer having an acid anhydride structure. In this case, modificationmay be carried out in the same manner as the above polymer (2).

[0032] Out of these polymers, the polymer having an acid anhydridestructure not in the main chain but only in the side chain (2) ispreferred, a polyolefin and a hydrogenated product of a diene(co)polymer modified by an dicarboxylic anhydride having a carbon-carbondouble bond are more preferred, and maleic anhydride modifiedpolyethylene, maleic anhydride modified polypropylene and maleicanhydride modified styrene-butadiene copolymer are particularlypreferred.

[0033] The acid value of the above polymer (B), that is, the amount (mg)of potassium hydroxide required for the neutralization of a free fattyacid contained in 1 g of a lipid is preferably 0.1 to 500 mg KOH/g, morepreferably 0.5 to 400 mg KOH/g, particularly preferably 1 to 300 mgKOH/g.

[0034] When the acid value is smaller than 0.1 mg KOH/g, no hydrophilicnature is obtained and the removal rate may lower. When the acid valueis larger than 500 mg KOH/g, hygroscopicity is extremely rised, wherebythe hardness of the polishing pad may be lowered by moisture absorptiondisadvantageously.

[0035] As for this acid value, the acid anhydride group is ring-openingunder the measurement conditions of this acid value and calculated as anacid.

[0036] The above component (B) is generally dispersed in the component(A) as an island to form a sea-island structure as a whole, and thesecomponents form a matrix.

[0037] As for the amounts of the component (A) and the component (B),the amount of the component (A) is 70 to 99.9 mass %, preferably 75 to99.5 mass %, more preferably 80 to 99 mass %, and the content of thecomponent (B) is 0.1 to 30 mass %, preferably 0.5 to 25 mass %, morepreferably 1 to 20 mass % based on 100 mass % of the total of thecomponents (A) and (B). When the amount of the component (B) is smallerthan 0.1 mass %, the effect of improving the removal rate may not befully obtained. When the amount of the component (B) is larger than 30mass %, the effect of improving the removal rate is saturated and themoldability and strength of the polishing pad formed from the resultingcomposition may lower according to the substances contained.

[0038] In the present invention, optionally, a hydrophilic substancehaving a functional group which differs from the components (A) and (B)may be contained in the matrix comprising the above components (A) and(B) to improve compatibility with slurry.

[0039] The hydrophilic substance having a functional group is a(co)polymer of a monomer(s) having a functional group, or a polymerobtained by modifying the same material as the above component (A) withat least one selected from carboxyl group, hydroxyl group, epoxy groupand amino group. This polymer may or may not be crosslinked butpreferably crosslinked. As the hydrophilic substance is preferably useda polymer obtained by polymerizing monomers having a functional group ora polymer having an extremely high content of a functionalgroup-containing component, for example, a polymer comprising a monomerhaving a functional group in an amount of 80 mol % or more, as describedhereinafter.

[0040] The above (co)polymer of a monomer(s) having a functional groupis, for example, a (co)polymer comprising (a) the polymerization unit ofa monomer having one polymerizable unsaturated group and at least onefunctional group selected from the group consisting of carboxyl group,amino group, hydroxyl group, epoxy group, sulfonic acid group andphosphoric acid group (to be referred to as “monomer (a)), and/or (b)the polymerization unit of a monomer having at least two polymerizableunsaturated groups (crosslinkable monomer, to be referred to as “monomer(b)” hereinafter), or a copolymer comprising the polymerization unit(s)of the above monomer (a) and/or the above monomer (b) and thepolymerization unit of other copolymerizable monomer.

[0041] Examples of the monomer having a carboxyl group as the monomer(a) include (1) unsaturated carboxylic acids such as (meth)acrylic acid,maleic acid, fumaric acid, itaconic acid, tetraconic acid and cinnamicacid, (2) free carboxyl group-containing esters such as monoesters of anonpolymerizable polycarboxylic acid such as phthalic acid, succinicacid or adipic acid and a hydroxyl group-containing unsaturated compoundsuch as (meth)allyl alcohol or 2-hydroxyethyl (meth)acrylate, and (3)salt compounds thereof. Out of these, unsaturated carboxylic acids arepreferred.

[0042] The monomer having an amino group is preferably a monomer havinga tertiary amino group, as exemplified by dialkylaminoalkyl(meth)acrylates such as dimethylaminomethyl (meth)acrylate,diethylaminomethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate,2-diethylaminoethyl (meth)acrylate, 2-(di-n-propylamino)ethyl(meth)acrylate, 2-dimethylaminopropyl (meth)acrylate,2-diethylaminopropyl (meth)acrylate, 2-(di-n-propylamino)propyl(meth)acrylate, 3-dimethylaminopropyl (meth)acrylate,3-diethylaminopropyl (meth)acrylate and 3-(di-n-propylamino)propyl(meth)acrylate; N-dialkylaminoalkyl group-containing unsaturated amidessuch as N-dimethylaminomethyl (meth)acrylamide, N-diethylaminomethyl(meth)acrylamide, N-(2-dimethylaminoethyl) (meth)acrylamide,N-(2-diethylaminoethyl) (meth)acrylamide, N-(2-dimethylaminopropyl)(meth)acrylamide, N-(2-diethylaminopropyl) (meth)acrylamide,N-(3-dimethylaminopropyl) (meth)acrylamide and N-(3-diethylaminopropyl)(meth)acrylamide; and tertiary amino group-containing vinyl aromaticcompounds such as N,N-dimethyl-p-aminostyrene,N,N-diethyl-p-aminostyrene, dimethyl(p-vinylbenzyl) amine,diethyl(p-vinylbenzyl) amine, dimethyl(p-vinylphenethyl)amine,diethyl(p-vinylphenethyl)amine, dimethyl(p-vinylbenzyloxymethyl)amine,dimethyl[2-(p-vinylbenzyloxy)ethyl]amine,diethyl(p-vinylbenzyloxymethyl)amine,diethyl[2-(p-vinylbenzyloxy)ethyl]amine,dimethyl(p-vinylphenethyloxymethyl)amine,dimethyl[2-(p-vinylphenethyloxy)ethyl]amine,diethyl(p-vinylphenethyloxymethyl)amine,diethyl[2-(p-vinylphenethyloxy)ethyl]amine, 2-vinylpyridine,3-vinylpyridine and 4-vinylpyridine. Out of these, dialkylaminoalkyl(meth)acrylates and tertiary amino group-containing vinyl aromaticcompounds are preferred.

[0043] Examples of the monomer having a hydroxyl group includehydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate,2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate and4-hydroxybutyl (meth)acrylate; mono(meth)acrylates of a polyalkyleneglycol (the number of alkylene glycol units is preferably 2 to 23) suchas polyethylene glycol and polypropylene glycol; hydroxylgroup-containing unsaturated amides such as N-hydroxymethyl(meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide andN,N-bis(2-hydroxyethyl) (meth)acrylamide; hydroxyl group-containingvinyl aromatic compounds such as o-hydroxystyrene, m-hydroxystyrene,p-hydroxystyrene, o-hydroxy-α-methylstyrene, m-hydroxy-α-methylstyrene,p-hydroxy-α-methylstyrene and p-vinylbenzyl alcohol; and (meth)allylalcohols. Out of these, hydroxylalkyl (meth)acrylates and hydroxylgroup-containing vinyl aromatic compounds are preferred.

[0044] Examples of the monomer having an epoxy group include (meth)allylglycidyl ether, glycidyl (meth)acrylate and 3,4-oxycyclohexyl(meth)acrylate.

[0045] Examples of the monomer having a sulfonic acid group include (1)(meth)acrylamide monomers such as 2-(meth)acrylamidoethanesulfonic acid,2-(meth)acrylamidopropanesulfonic acid,3-(meth)acrylamidopropanesulfonic acid,2-(meth)acrylamido-2-methylpropanesulfonic acid and3-(meth)acrylamido-2-methylpropanesulfonci acid; (2) (meth)acrylatemonomers such as ethyl (meth)acrylate 2-sulfonate, propyl (meth)acrylate2-sulfonate, propyl (meth)acrylate 3-sulfonate and ethyl (meth)acrylate1,1-dimethyl-2-sulfonate; (3) vinyl aromatic compounds monomers such asp-vinylbenzenesulfonic acid and p-isopropenylbenzenesulfonic acid; and(4) salt compounds thereof.

[0046] Examples of the monomer having a phosphoric acid group includephosphoric ethylene (meth)acrylate, phosphoric trimethylene(meth)acrylate, phosphoric tetramethylene (meth)acrylate, phosphoricpropylene (meth)acrylate, phosphoric bis(ethylene(meth)acrylate),phosphoric bis(trimethylene (meth)acrylate), phosphoricbis(tetramethylene (meth)acrylate), phosphoric diethylene glycol(meth)acrylate, phosphoric triethylene glycol (meth)acrylate, phosphoricpolyethylene glycol (meth)acrylate, phosphoric bis(diethylene glycol(meth)acrylate), phosphoric bis(triethylene glycol (meth)acrylate),phosphoric bis(polyethylene glycol (meth)acrylate) and salt compoundsthereof.

[0047] Examples of the above monomer (b) include ethylene glycoldi(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanedioldi(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropanedi(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritoltri(meth)acrylate, pentaerythritol tetra(meth)acrylate, divinylbenzene,diisopropenylbenzene and trivinylbenzene. They may be used alone or incombination of two or more.

[0048] The above hydrophilic substance can be manufactured by suitablycombining the above monomers (a) and (b) with a monomer other than themonomers (a) and (b). The polymerization of these monomers is notparticularly limited and may be radical (co)polymerization, anion(co)polymerization or cation (co)polymerization. The resulting copolymermay be a random copolymer, block copolymer or graft copolymer.

[0049] The amount of the above hydrophilic substance is preferably 50mass % or less, more preferably 30 mass % or less, particularlypreferably 15 mass % or less based on 100 mass % of the total of theabove components (A) and (B) and the hydrophilic substance.Theyformamatrix, that is, a medium for dispersing water-solubleparticles, etc.

[0050] A water-soluble substance (C) is preferably dispersed in thematrix material (resin material) comprising the above components (A) and(B) and optionally the above hydrophilic substance.

[0051] The water-soluble substance (C) can form pores for holding slurrywhen polishing is carried out with the slurry after it is released fromthe surface of the matrix material by its contact with water. Theaverage pore diameter of the pores formed after the water-solublesubstance is released from the polishing pad, that is, the size (averagediameter) of this water-soluble substance contained in the matrix beforerelease is preferably 0.1 μm to 500 μm, more preferably 0.5 μm to 300μm, much more preferably 5 μm to 100 μm.

[0052] The water-soluble substance includes what is swollen or gelled byits contact with water and can be thereby released, such as awater-absorbing resin besides a water-soluble substance such as awater-soluble polymer. This water-soluble substance may dissolve orswell in a medium comprising water as the main component, methanol, etc.This water-soluble substance is generally dispersed in the matrixmaterial as a dispersion.

[0053] The water-soluble substance (C) is generally solid but may beliquid. The solid water-soluble substance may be particulate, fibroussuch as whisker-shaped or linear, or odd-shaped such as tetrapod-shaped.

[0054] The average particle diameter of the water-soluble particles is,for example, 0.1 μm to 500 μm, preferably 0.5 μm to 300 m, morepreferably 5 μm to 100 μm. When this average particle diameter issmaller than 0.1 μm, the formed pores are small and a polishing padwhich can hold abrasive particles completely may not be obtained. Whenthe average particle diameter is larger than 500 μm, the mechanicalstrength of the obtained polishing pad may lower. The average particlediameter is the average value of the maximum lengths of thewater-soluble substances contained in the matrix.

[0055] This water-soluble substance (C) may be organic or inorganic. Itis preferably organic.

[0056] Examples of the organic water-soluble substance include dextrin,cyclodextrin, mannitol, saccharides such as lactose, celluloses such ashydroxypropyl cellulose and methyl cellulose, starch, protein, polyvinylalcohol, polyvinyl pyrrolidone, polyvinyl sulfonic acid, polyacrylicacid, polyethylene oxide, water-soluble photosensitive resin andsulfonated polyisoprene. They may used alone or in combination of two ormore.

[0057] Examples of the inorganic water-soluble substance includepotassium acetate, potassium nitrate, potassium carbonate, potassiumhydrogencarbonate, potassium bromide, potassium phosphate, potassiumsulfate, magnesium sulfate, magnesium nitrate and calcium nitrate. Theymay be used alone or in combination of two or more.

[0058] Further, the liquid water-soluble substance is not limited to aparticular kind but preferably has no bad influence upon polishingefficiency by dissolution into the slurry during polishing. Examples ofthe liquid water-soluble substance include organic acids such as formicacid, acetic acid, and oxidizing agents such as aqueous solution ofhydrogen peroxide, aqueous solution of peracetic acid and nitric acid.

[0059] The amount of the water-soluble substance (C) is preferably 50vol % or less, more preferably 0.1 to 40 vol %, much more preferably 1to 30 vol %, particularly preferably 1 to 20 vol % based on 100 vol % ofthe above matrix material. When the amount of the water-solublesubstance (C) is larger than 50 vol %, the hardness and mechanicalstrength of the obtained polishing pad may not be maintained atappropriate values.

[0060] The water-soluble substance (C) is dispersed in the matrixmaterial. In the polishing pad obtained from this composition for apolishing pad, pores are formed by the dissolution of the water-solublesubstance (C) existent in the outermost surface layer when it contactswater. The pores hold the slurry and retain the residual dust afterpolishing temporarily. The water-soluble substance dissolves or swellsand releases from the matrix material when it contact the slurry whichis an aqueous dispersion in the polishing pad.

[0061] It is preferred that the water-soluble substance (C) shoulddissolve in water only when it is exposed to the surface layer of thepolishing pad and should not absorb moisture or swell when it isexistent in the interior of the polishing pad. Therefore, thewater-soluble substance (C) preferably has an outer shell forsuppressing moisture absorption on at least part of its outermostportion. This outer shell may be physically adsorbed to thewater-soluble substance (C), chemically bonded to the water-solublesubstance (C), or in contact with the water-soluble substance (C) byphysical adsorption and chemical bonding. The outer shell is made ofepoxy resin, polyimide, polyamide or polysilicate. Even when it isformed on only part of the water-soluble substance (C), the above effectcan be fully obtained.

[0062] In the polishing pad, the above water-soluble substance (C) hasthe function of increasing the hardness of the polishing pad in additionto the function of forming pores. For instance, the Shore D hardness ofthe entire polishing pad is increased to 35 to 100. Pressure to beapplied to the surface to be polished on the polishing pad can be madelarge by increasing this hardness of the polishing pad. As a result, notonly the removal rate is improved but also high planarity is obtained.Therefore, this water-soluble substance (C) is particularly preferably asolid substance which can ensure sufficiently high hardness for thepolishing pad.

[0063] At least one of an oxidizing agent, organic acid, alkali metalhydroxide and acid, pH modifier, surfactant and scratch prevention agentall of which have been contained in slurry may be contained in thepolishing pad of the present invention. Thereby, when this polishing padis used, polishing can be carried out by supplying only water at thetime of polishing. However, it is preferred that an abrasive andpolyvalent metal ion which have been contained in slurry should not becontained. Further, various additives such as a filler, softening agent,antioxidant, ultraviolet light absorber, antistatic agent, lubricant orplasticizer may be optionally contained in the polishing pad of thepresent invention.

[0064] The above oxidizing agent may be used without restriction if itis water-soluble. Examples of the oxidizing agent include organicperoxides such as hydrogen peroxide, peracetic acid, perbenzoic acid andtert-butyl hydroperoxide, permanganic acid compounds such as potassiumpermanganate, bichromic acid compounds such as potassium bichromate,halogen acid compounds such as potassium iodate, nitric acid and nitricacid compounds such as iron nitrate, perhalogen acid compounds such asperchloric acid, transition metal salts such as potassium ferricyanide,persulfates such as ammonium persulfate, polyvalent metal salts such asiron nitrate and cerium ammonium nitrate, and heteropolyacids such astungstosilicic acid, tungstophosphoric acid molybdosilicic acid andmolybdophosphoric acid. They may be used in combination of two or more.Out of these, hydrogen peroxide and organic peroxides which do notcontain metal element and whose decomposed products are harmless areparticularly preferred. When a metal layer such as a film to be polishedof a wafer is to be polished, the removal rate can be greatly improvedby adding the oxidizing agent.

[0065] Based on 100 parts by mass (to be simply referrers to as “parts”hereinafter) of the entire polishing pad, the amount of the oxidizingagent is preferably 0 to 10 parts, particularly preferably 0 to 5 parts.

[0066] The above organic acid can stabilize the above oxidizing agentand further improve the removal rate. Examples of the organic acidinclude paratoluenesulfonic acid, dodecylbenzenesulfonic acid,isoprenesulfonic acid, gluconic acid, lactic acid, citric acid, tartaricacid, malic acid, glycolic acid, malonic acid, formic acid, oxalic acid,succinic acid, fumaric acid, maleic acid and phthalic acid. Out ofthese, gluconic acid, lactic acid, citric acid, tartaric acid, malicacid, glycolic acid, malonic acid, formic acid, oxalic acid, succinicacid, fumaric acid, maleic acid and phthalic acid are preferred.Further, out of these, tartaric acid, malic acid, succinic acid andphthalic acid are particularly preferred. These organic acids may beused alone or in combination of two or more. The amount of the organicacid contained in the whole pad is preferably 0 to 10 parts,particularly preferably 0 to 5 parts based on 100 parts of the wholepad. When an organic acid is used as the water-soluble substance asdescribed above, this organic acid may not be contained and when a largeamount of the water-soluble substance is required, the organic acid maybe contained. Further, tartaric acid, malic acid, succinic acid orphthalic acid all of which are preferred and solid may be blended.

[0067] The above surfactant is a cationic, anionic or nonionicsurfactant. Examples of the cationic surfactant include aliphatic aminesalts and aliphatic ammonium salts. Examples of the anionic surfactantinclude fatty acid soap; carboxylates such as alkyl ether carboxylates;sulfonates such as alkylbenzene sulfonates, allkylnaphthalene sulfonatesand α-olefin sulfonates; sulfates such as higher alcohol sulfates, alkylether sulfates and polyoxyethylene alkylphenyl ethers; and phosphatessuch as alkyl phosphates. Examples of the nonionic surf actant includeethers such as polyoxyethylene alkyl ethers, ether esters such aspolyoxyethylene ethers of a glycerin ester, and esters such aspolyethylene glycol fatty acid esters, glycerin esters and sorbitanesters. The amount of the surfactant contained in the whole pad ispreferably 0 to 10 parts, particularly preferably 0 to 5 parts based on100 parts of the whole pad.

[0068] Examples of the above filler include materials for improvingstiffness such as calcium carbonate, magnesium carbonate, talc and clay,and materials having a polishing effect such as manganese dioxide,dimanganese trioxide and barium carbonate.

[0069] The method of manufacturing this polishing pad is notparticularly limited. When the method comprises a mixing step, mixingcan be carried out with a known mixer such as a roll, kneader, Banburymixer or extruder (single-screw or multi-screw). The mixed compositionfor a polishing pad can be processed into a desired form such as asheet, block or film by press molding, extrusion molding or injectionmolding. This is cut to a desired size to obtain a polishing pad.

[0070] The method of dispersing the water-soluble substance into thematrix material is not particularly limited.

[0071] In general, the matrix material, the water-soluble substance andother additives are mixed together. The matrix material is mixed underheating so that it can be easily processed. The water-soluble substanceis preferably solid at the mixing temperature. When the water-solublesubstance is solid, it is easily dispersed while it has the abovepreferred average particle diameter irrespective of its compatibilitywith the above matrix material. Therefore, the type of the water-solublesubstance is preferably selected according to the processing temperatureof the matrix material in use.

[0072] The specific gravity of the polishing pad is preferably 0.9 to1.2, particularly preferably 0.95 to 1.15. When the specific gravity islower than 0.9, pressure to be applied to the material to be polishedduring polishing tends to lower and planarity may not becomesatisfactory. When the specific gravity is higher than 1.2, crosslinkingis apt to proceed excessively and the removal rate may lower.

[0073] The Shore D hardness of the polishing pad is preferably 35 ormore, more preferably 50 to 90, much more preferably 55 to 85 andgenerally 100 or less. When the Shore D hardness is lower than 35,pressure to be applied to the material to be polished during polishingtends to lower, the removal rate drops and planarity may not becomesatisfactory.

[0074] Grooves and a dot pattern may be optionally formed in apredetermined form on the polishing surface of the polishing pad inorder to improve the delivery efficiency of the slurry. Further, apolishing pad having a multi-layer structure may be obtained by forminga soft layer on the rear surface, that is, the surface opposite to thepolishing surface of the polishing pad. This polishing pad is notlimited to a particular shape and may be disk-like, belt-like orroller-like according to a polishing machine.

[0075] The polishing pad of the present invention can be used to polishthe surface of a material to be polished (also referred to as “film tobe processed”). According to this polishing method, chemical mechanicalpolishing which provides excellent planarity can be carried out andfurther a higher removal rate can be obtained.

[0076] The material to be polished is not particularly limited andvarious materials may be used. Examples of the film to be processedinclude a silicon oxide film (silica film), amorphous silicon film,polycrystal silicon film, monocrystal silicon film, silicon nitridefilm, pure tungsten film, pure aluminum film, pure copper film and filmmade of an alloy of tungsten, aluminum or copper and other metal formedon a wafer in the process of manufacturing a semiconductor device suchas VLSI. A film made of an oxide or nitride of a metal such as tantalumor titanium may also be used.

[0077] The polishing pad of the present invention is advantageously usedin chemical mechanical polishing for the formation of buried metalwiring, the isolation of micro-device and the flattening of aninterlayer insulating film.

[0078] The material to be polished for the formation of buried metalwiring is a substrate (which generally comprises at least a wafer and aninsulating film formed on the front surface of the wafer, and mayfurther comprise a barrier metal layer on the insulating film) havinggrooves at least on the front surface, that is, a substrate which willbecome a semiconductor device. In other words, it is a laminate having adesired material buried in the grooves. For the polishing of thismaterial to be polished, the excessively buried material can be removedby the chemical mechanical polishing step using the polishing pad of thepresent invention to flatten the surface of the material. When thematerial to be polished has the barrier metal layer below the buriedmaterial, the barrier metal layer can be polished in the latter stage ofthe chemical mechanical polishing. After the excess buried material andthe excess barrier metal layer optionally formed are removed, part ofthe insulating film may be optionally removed by overpolishing.

[0079] This buried type laminate is as shown in FIG. 1, for example.

[0080] That is, a laminated substrate 1 comprises a substrate 11 made ofsilicon or the like, an insulating film 12 formed on the siliconsubstrate 11, an insulating film 13 formed on the insulating film 12, aninsulating film 14 formed on the insulating film 13 to form a groove,and a barrier metal film 15 formed to cover the insulating film 14 andthe groove, and a film 16 made of a wiring material formed on the abovebarrier metal film 15 and fill the above groove (the surface of thewiring material is an uneven surface corresponding to the uneven surfaceof the insulating film).

[0081] The material to be polished for the isolation of micro-device isa material having a sectional structure as shown in FIG. 2(a), forexample. This material may comprise a substrate 21 made of silicon, etal, and having an uneven surface, a stopper layer 22 formed on theprojection portions of the substrate 21 and a buried insulating layer 23formed to cover the depressed portions of the above substrate 21 and thestopper layer 22.

[0082] For the polishing of this material to be polished, the projectionportions of the insulating layer 23 are removed, and the insulatinglayer 23 is flattened until the top portions of the stopper layer 22 areexposed to obtain a sectional form as shown in FIG. 2(b).

[0083] The material to be polished for the flattening of an interlayerinsulating film is a material having a sectional structure as shown inFIG. 3(a). This material comprises a substrate 31 made of silicon, etal, an insulating film 32 formed on the substrate 31, wiring materials33 formed on the insulating film 32, and an interlayer insulating film34 formed to cover the wiring materials 33 and portions in theinsulating film 32 where the wiring materials 33 are not formed.

[0084] For the polishing of the above material, the projection portionsof the interlayer insulating film 34 are flattened without exposing thewiring materials 33, and a sectional structure shown in FIG. 3(b) isobtained after polishing.

[0085] Examples of the insulating material for forming the aboveinsulating films 12, 14, 23 and 32 and the interlayer insulating film 34include a silicon oxide (SiO₂) film, boron phosphorus silicate film(BPSG film) formed by adding small mounts of boron and phosphorus toSiO₂, insulating film called “FSG (Fluorine-doped Silicate Glass)”formed by doping SiO₂ with fluorine, and silicon oxide-based insulatingfilm having a low dielectric constant.

[0086] Examples of the silicon oxide film include a thermal oxide film,PETEOS (Plasma Enhanced-TEOS) film, HDP (High Density PlasmaEnhanced-TEOS) film and silicon oxide film obtained by thermal CVD.

[0087] The above thermal oxide film can be formed by exposing siliconheated at a high temperature to an oxidizing atmosphere in order tochemically react silicon with oxygen or silicon with water.

[0088] The above PETEOS film can be formed from tetraethyl orthosilicate(TEOS) by chemical vapor deposition using plasma for promoting areaction.

[0089] The above HDP film can be formed from tetraethyl orthosilicate(TEOS) by chemical vapor deposition using high-density plasma forpromoting a reaction. The above silicon oxide film obtained by thermalCVD can be obtained by normal-pressure CVD (AP-CVD) or low-pressure CVD(LP-CVD).

[0090] The above boron phosphorus silicate (BPSG) film can be obtainedby normal-pressure CVD (AP-CVD) or low-pressure CVD (LP-CVD).

[0091] The above insulating film called “FSG (Fluorine doped SilicateGlass)” can be formed by chemical vapor deposition using high-densityplasma for promoting a reaction.

[0092] Further, the above silicon oxide-based insulating film having alow dielectric constant can be obtained by applying a raw material to asubstrate by spin-coating and heating the coating film in an oxidizingatmosphere. Examples of the silicon oxide-based insulating film having alow dielectric constant include HSQ (Hydrogen Silsesquioxane) filmcomprising triethoxysilane, and MSQ (Methyl Silsesquioxane) filmcomprising methyl trimethoxysilane in addition to tetraethoxysilane.Insulating films having a low dielectric constant made of an organicpolymer such as polyarylene-based polymer, polyarylene ether-basedpolymer, polyimide-based polymer or benzocyclobutene polymer may also beused.

[0093] The above barrier metal film 15 is made of tantalum, tantalumnitride, tungsten nitride, titanium or titanium nitride.

[0094] The above insulating film 13 and the stopper layer 22 are made ofsilicon nitride, et al.

[0095] The above wiring materials 16 and 33 are made of copper, aluminumor tungsten. Copper, aluminum and tungsten include not only pure metalsbut also alloys containing 90% or more of the respective metals.

[0096] In the chemical mechanical polishing method of the presentinvention, polishing machines such as the EPO-112 and EPO-222 of EbaraCorporation, the LGP-510 and LGP-552 of Lap Master SFT Co., Ltd., theMirra of Applied Material Co., Ltd., the Teres of Ram Research Co.,Ltd., and the AVANTI 472 of Speed Fam-IPEC Co., Ltd. may be used.

[0097] In these polishing machines, the material to be polished isbrought into slide contact with the surface of a polishing pad on whichabrasive particles such as an aqueous dispersion for chemical mechanicalpolishing are dispersed, and while bringing into slide the aqueousdispersion for chemical mechanical polishing which is an abrasive isdropped from above (slurry feed unit, etc.) to polish the material.Preferably, this aqueous dispersion for chemical mechanical polishingsuitable for each material to be polished is selected and the materialsfor forming this aqueous dispersion are not particularly limited. Thematerials include water, abrasive grains, oxidizing agent, alkali metalhydroxide and acid, ph modifier, surfactant and scratch preventingagent. They may be used alone or in combination of two or more.

EXAMPLES

[0098] The following examples are given to further illustrate thepresent invention.

[0099] Manufacture of Polishing Pad:

Example 1

[0100] 90 mass % of (a) 1,2-polybutadiene (JSR RB830 of JSRCorporation), 10 mass % of (b) maleic anhydride modified polypropylene(Umex 1010 having an acid value of 52 mg KOH/g of Sanyo ChemicalIndustries, Ltd.) and 5 vol % based on the total of the above components(a) and (b) of (c) β-cyclodextrin (Dexy Pearl β-100 of Bio ResearchCorporation of Yokohama) as a water-soluble substance were mixedtogether by a kneader heated at 120° C. Thereafter, an organic peroxide(Percumyl D40 of NOF Corporation) was added in an amount of 1 part bymass based on 100 parts by mass of the total of the above components (a)and (b) and further mixed. Then, a crosslinking reaction was carried outin a metal mold at 170° C. for 18 minutes to mold a polishing pad havinga diameter of 60 cm and a thickness of 2.8 mm (specific gravity of0.95). Concentric grooves having a width of 0.5 mm, a pitch of 2 mm anda depth of 1.4 mm were formed in one surface of this molded product ofthe pad by a cutting machine (of Kato Machinery Co., Ltd.).

Example 2

[0101] 70 mass % of (a) 1,2-polybutadiene which was used in Example 1,30 mass % of (b) a hydrogenated product of maleic anhydride modifiedstyrene-butadiene-styrene block copolymer (trade name: Taftec 1911having an acid value of 2 mg CH₃ONa/g (equivalent to 2.07 mg KOH/g) ofAsahi Chemical Industry Co., Ltd.) and 20 vol % based on the total ofthe above components (a) and (b) of (c) the water-soluble substancewhich was used in Example 1 were mixed together by a kneader heated at120° C. Thereafter, a polishing pad (specific gravity of 1.08) wasobtained in the same manner as in Example 1 except that the organicperoxide which was used in Example 1 was added in an amount of 1 part bymass based on 100 parts by mass of the above component (a).

Example 3

[0102] 98 mass % of (a) 1,2-polybutadiene which was used in Example 1, 2mass % of (b) maleic anhydride modified polypropylene (trade name: Umex1001 having an acid value of 26 mg KOH/g of Sanyo Chemical Industries,Ltd.) and 1 vol % based on the total of the above components (a) and (b)of (c) the water-soluble substance which was used in Example 1 weremixed together by a kneader heated at 120° C. Thereafter, a polishingpad (specific gravity of 0.94) was obtained in the same manner as inExample 1 except that the organic peroxide which was used in Example 1was added in an amount of 1 part by mass based on 100 parts by mass ofthe above component (a).

Example 4

[0103] 90 mass % of (a) 1,2-polybutadiene which was used in Example 1,10 mass % of (b) maleic anhydride modified polyethylene (trade name:Umex 2000 having an acid value of 30 mg KOH/g of Sanyo ChemicalIndustries, Ltd.) and 5 vol % based on the total of the above components(a) and (b) of (c) the water-soluble substance which was used in Example1 were mixed together by a kneader heated at 120° C. Thereafter, apolishing pad (specific gravity of 0.95) was obtained in the same manneras in Example 1 except that the organic peroxide which was used inExample 1 was added in an amount of 1 part by mass based on 100 parts bymass of the above component (a).

Comparative Example 1

[0104] 70 vol % of (a) 1,2-polybutadiene which was used in Example 1 and30 vol % of (c) the water-soluble substance which was used in Example 1were mixed together by a kneader heated at 120° C. Thereafter, apolishing pad (specific gravity of 0.96) was obtained in the same manneras in Example 1 except that the organic peroxide which was used inExample 1 was added in an amount of 1 part by mass based on 100 parts bymass of the above component (a).

Comparative Example 2

[0105] 99 mass % of (a) 1,2-polybutadiene which was used in Example 1, 1mass % of (b) polybutadiene having a hydroxyl group at both terminals(trade name: NISSO-PB G3000 of Nippon Soda Co., Ltd.) and 30 vol % basedon the total of the above components (a) and (b) of (c) thewater-soluble substance which was used in Example 1 were mixed togetherby a kneader heated at 120° C. Thereafter, a polishing pad (specificgravity of 1.07) was obtained in the same manner as in Example 1 exceptthat the organic peroxide which was used in Example 1 was added in anamount of 1 part by mass based on 100 parts by mass of the total of theabove components (a) and (b).

Comparative Example 3

[0106] Butadiene, acrylonitrile, methacrylic acid, 2-hydroxybutylmethacrylate, ethylene glycol dimethacrylate and divinylbenzene wereemulsion polymerized in a molar ratio of 62/20/5/11/1/2 in the presenceof sodium laurylsulfate as an emulsifier and benzoyl peroxide as apolymerization initiator. The obtained copolymer emulsion was thensolidified and dried to prepare a copolymer having a functional group(d). The polymerization conversion was almost 100%.

[0107] Thereafter, 90 mass % of (a) 1,2-polybutadiene which was used inExample 1, 8 mass % of (e) polybutadiene rubber (trade name: BROL of JSRCorporation), 2 mass % of (d) the above prepared copolymer having afunctional group and 30 vol % based on the total of the above components(a), (d) and (e) of (c) the water-soluble substance which was used inExample 1 were mixed together by a kneader heated at 120° C. Thereafter,a polishing pad (specific gravity of 1.05) was obtained in the samemanner as in Example 1 except that the organic peroxide which was usedin Example 1 was added in an amount of 1 part by mass based on 100 partsby mass of the total of the above components (a), (d) and (e).

[0108] Evaluation of Polishing Efficiency:

[0109] (1) Evaluation of Removal Rate

[0110] The polishing pads obtained in Examples 1 to 4 and ComparativeExamples 1 to 3 were each set on the platen of a polishing machine (LapMaster LGP510 of SFT Co., Ltd.), copper film and silica film wafers werepolished at a platen revolution of 50 rpm and a slurry flow rate of 100ml/min to evaluate differences in polishing efficiency among thepolishing pads, and the obtained results are shown in Tables 1 and 2.The CMS1101 (of JSR Corporation) was used as slurry for the thermaloxide film wafer (silica) and the iCUe5003 (of Cabot Co., Ltd.) was usedas slurry for the copper film wafer. The removal rate was obtained bymeasuring a change in film thickness with an optical film thicknessmeter.

[0111] (2) Evaluation of Dishing

[0112] Semiconductor wafers (polishing test wafers which differ inwiring width and space width: trade name: SKW-7 of SKW Co., Ltd.) werepolished under the following conditions and the dishings of thesemiconductor wafers were measured at line-and-space distances of 250 μmand 250 μm by a Profilar (P-10 of KLA-Tencor Ltd.). The results areshown in Table 1.

[0113] Slurry; CMS1101 (JSR Corporation)

[0114] Chemical mechanical polishing machine: EP0112 (Ebara Corporation)

[0115] Slurry flow rate; 200 ml/min

[0116] Polishing load; 400 g/cm²

[0117] Platen revolution; 70 rpm

[0118] Head revolution; 70 rpm

[0119] Removal rate; 400 nm/min

[0120] Polishing time; 5.75 minutes (15% overpolishing) TABLE 1 Removalrate of thermal Removal rate Acid value of Shore D oxide film of Cu filmDishing component B hard- (Å/min) (Å/min) (nm) (mg KOH/g) ness Ex. 11850 5300 40 52 63 C. Ex. 1 1050 3000 180 — 72 C. Ex. 2 1340 3300 110 —71 C. Ex. 3 1440 4000 95 — 68

[0121] TABLE 2 Removal rate of Removal rate of thermal oxide film Cufilm Dishing Shore D (Å/min) (Å/min) (nm) hardness Ex. 2 1920 5830 50 65Ex. 3 1650 5170 50 60 Ex. 4 1750 5250 40 62

[0122] According to Table 1, the removal rates of a silica film and acopper film with the polishing pad of Comparative Example 1 in whichnone of acid anhydride group, carboxyl group or hydroxyl group wascontained were 1,050 Å/min and 3,000 Å/min, respectively. In ComparativeExample 2 in which polybutadiene having a hydroxyl group at bothterminals was used, the removal rates of a silica film and a copper filmwere 1,340 Å/min and 3,300 Å/min, respectively. In Comparative Example 3in which a copolymer having a carboxyl group was used, the removal ratesof a silica film and a copper film were 1,440 Å/min and 4,000 Å/min,respectively.

[0123] In Example 1 in which a polymer having an acid anhydride groupwas contained, the removal rates of a silica film and a copper film were1,850 Å/min and 5,300 Å/min which were 1.76 times and 1.76 times thoseof Comparative Example 1, respectively. Further, in Comparative Examples2 and 3, the removal rates of a silica film and a copper film werehigher than those of Comparative Example 1 in which no functional groupwas contained but lower than those of Example 1. That is, the removalrates of Example 1 were 1.38 times and 1.60 times higher than those ofComparative Example 2 and 1.28 times and 1.33 times higher than those ofComparative Example 3.

[0124] The dishing of Comparative Example 1 was 180 nm (4.5 times thatof Example 1), the dishing of Comparative Example 2 was 110 nm (2.75times that of Example 1), the dishing of Comparative Example 3 was 95 nm(1.33 times that of Example 1) and the dishing of Example 1 wasextremely small at 40 nm.

[0125] It is understood from above that the polishing pad of Example 1has a higher removal rate for both a silica film and a copper film andsmall dishing. Thus, it was found that the polishing pad of Example 1has excellent polishing efficiency.

[0126] It is understood from Table 2 that the polishing pads of Examples2 to 4 have the same excellent properties as the polishing pad ofExample 1.

[0127] As described above, it is seen that the polishing pad of thepresent invention has a high removal rate and excellent polishingefficiency for both an insulating film and a metal film.

What is claimed is:
 1. A polishing pad comprising 70 to 99.9 mass % of(A) a crosslinked diene elastomer and 0.1 to 30 mass % of (B) a polymerhaving an acid anhydride structure based on 100 mass % of the total ofthe components (A) and (B) and having a specific gravity of 0.9 to 1.2.2. The polishing pad of claim 1, wherein the crosslinked diene elastomer(A) is a crosslinked butadiene elastomer or crosslinked isopreneelastomer.
 3. The polishing pad of claim 1, wherein the polymer havingan acid anhydride structure (B) is a polymer having an acid anhydridestructure only in the main chain, a polymer having an acid anhydridestructure only in the side chain or a polymer having an acid anhydridestructure in both the main chain and the side chain.
 4. The polishingpad of claim 3, wherein the polymer having an acid anhydride structureonly in the main chain is a (co)polymer of at least one unsaturateddicarboxylic anhydride selected from the group consisting of maleicanhydride, itaconic anhydride, citraconic anhydride andendomethylenetetrahydrophthalic anhydride, or a copolymer of at leastone unsaturated dicarboxylic anhydride and a monomer having no acidanhydride structure.
 5. The polishing pad of claim 3, wherein thepolymer having an acid anhydride structure only in the side chain is apolymer obtained by modifying a polymer having no acid anhydridestructure with at least one unsaturated dicarboxylic anhydride selectedfrom the group consisting of maleic anhydride, itaconic anhydride,citraconic anhydride and endomethylenetetrahydrophthalic anhydride. 6.The polishing pad of claim 3 or 5, wherein the polymer having an acidanhydride structure only in the side chain is maleic anhydride modifiedpolyethylene, maleic anhydride modified polypropylene or maleicanhydride modified styrene-butadiene copolymer.
 7. The polishing pad ofclaim 3, wherein the polymer having an acid anhydride structure in boththe main chain and the side chain is a polymer obtained by modifying apolymer having an acid anhydride structure only in the main chain withat least one unsaturated dicarboxylic anhydride selected from the groupconsisting of maleic anhydride, itaconic anhydride, citraconic anhydrideand endomethylenetetrahydrophthalic anhydride.
 8. The polishing pad ofclaim 1, wherein the acid value of the polymer having an acid anhydridestructure (B) is 0.1 to 500 mg KOH/g.
 9. The polishing pad of claim 1,wherein the crosslinked diene elastomer (A) and the polymer having anacid anhydride structure (B) form a matrix material and a water-solublesubstance (C) is further contained in the matrix material.
 10. Achemical mechanical polishing method comprising flattening the surfaceof a material to be polished by chemical mechanical polishing with thepolishing pad of claim 1.